This invention relates to an extension support unit effective when used for photographing, picturing, monitoring, inspecting, measuring, repairing or observing, from a high place, sport games, various kinds of event, disaster scenes, important installations, industrial facilities, buildings, animals, plants, and other objects, or for illumination or radio wave relaying, or when used as a support for standing a high column such as an electric pole, an antenna mast, a cable way support, a tent support and the like.
Conventionally, as an ordinary means for these purposes, a fixed support pole is installed, a temporary scaffold is assembled or a special truck crane is used.
Some extension poles has been provided but the use of them is restricted because they have various shortcomings.
For example, if a fixed support pole is installed for illumination on a golf course in the nighttime according to the prior art, it impairs the view in the daytime and is inconvenient in terms of maintenance. Also, the provision of a structure capable of resisting a wind force at a speed of, e.g., 60 m/sec in conformity with a regulation is disadvantageous in terms of economy. In the case of assembly of a temporary scaffold, there are restrictions in terms of siting, assembly, and removal of the scaffold require a long time and a great deal of labor, and there are, therefore, the problems of poor economy and difficulty of speedy adaptation. Special apparatus including a truck crane are not widely applicable because they are disadvantageous in terms of cost and ease of use.
With respect to extension poles based on the conventional methods, in a pneumatic type or hydraulic type extension pole, a shielding for preventing leakage of the medium is required and the structure of the pole must be strong. It is therefore difficult to increase the length of the pole.
In other types of extension pole based on the method of utilizing a hinge, the slide method using a wire and the mechanical fitting method, the support structure is complicated and the length of the support pole and the load imposed on the pole are considerably limited.